let obj = {
  a: 123,
  b: 234
}
let arr = [1, 2, 3]
let keys = Object.keys(arr)
let map = new Map()
map.set('a', [1, 2, 3])
map['b'] = [1, 2, 3]
let mapKeys = Object.keys(map)
console.log(mapKeys);